


C'mon babe, light my burner.

by ValkyrieOfSmut



Series: One shots [15]
Category: Undertale (Video Game)
Genre: Alternate Universe - College/University, Alternate Universe - Soulmates, Angst, Angst and Fluff and Smut, Angst with a Happy Ending, Ecto-Penis (Undertale), Explicit Sexual Content, F/M, Penis In Vagina Sex, Post-Undertale Pacifist Route, Soulmates, Undertale Monsters on the Surface, Vaginal Fingering, Vaginal Sex, implied add/adhd reader
Language: English
Status: Completed
Published: 2020-10-11
Updated: 2020-10-11
Packaged: 2021-03-07 20:28:48
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 2
Words: 8,779
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26943694
Author URL: https://archiveofourown.org/users/ValkyrieOfSmut/pseuds/ValkyrieOfSmut
Summary: Sans has to go to an accredited college to prove his degrees (basically take tests to prove that his degrees match the standards of the human education system). While he's there, he finds his soulmate, but fucks it up... Can Papyrus help him fix it, or is it broken for good?Aka, the Great Papyrus is great at solving puzzles and so good at japes that he tricks people into doing things without them realizing. Our hero!
Relationships: Sans (Undertale) & Reader, Sans (Undertale)/Reader
Series: One shots [15]
Series URL: https://archiveofourown.org/series/1396591
Comments: 14
Kudos: 187





	1. Where Sans finds his soulmate, and also fucks it all up...

**Author's Note:**

> This started out as a thought at work... an angst prompt, if you will... Listening to "Light my fire" by the Doors (and also there's a joke about another group singing it called someone and the bunsen burners), I thought what a pickup line... Sans would totally use that next to a bunsen burner lol... And then the prompt was born; what if (character) found their soulmate in chemistry class as partners, used that line, and then, while making out, asked them (for some reason) if they were only being with them because of some way they were different than them? (like reader being human and Sans being a monster.)  
> And then I made it smut, because I'm me...  
> Anyone is allowed to use this prompt, and please tag me- I'd love to read it if you make something of it!! 💖  
> Also, it's so long, I cut it in half, so instead of a one shot, it's a "Double tap". There's reasoning; Zombieland, mostly... "make sure it's done" lol.

**Summary for the Chapter:**

> And deals with all the angst of his fuck up, with a soulmate that doesn't want to talk to him.

**Notes for the Chapter:**

> It's implied that (Y/n) has ADD. Also, I write it funny, I guess. All of the tags on here say ADD/ADHD, but I shorthand it to AD/HD... though that might just be because I've had to write it a bunch... because I have ADD...  
> Hope you enjoy!!!!

(Y/n) sat in class, watching as her hand moved across the page as she copied down the notes in her general sciences class. 

Having to take general sciences wasn't too bad; you got to switch around a bit so you didn't have to keep doing the same thing all the time, helpful for people with AD/HD. She was actually nervous about having to do a whole year of the same type of science the next year. 

There was a bit of a commotion, urgent whispers starting up around her as the sound of the door opening stopped the professor in his pacing and lecturing. 

The dean of the school was there, in their classroom, having a hushed conversation with their teacher. 

It was impossible to hear what was being said from her spot so far away, but if he was there, it must have been something big. 

The professor leaned away in surprise and (Y/n)'s eyes narrowed as she watched their body language. 

It was definitely something big. 

The dean walked back across the room to the door as the professor straightened himself out. 

"Everyone, attention. Attention, please." He cleared his throat, looking confused for a moment. "This isn't- we, uh… We don't usually stop class to introduce new students, but this is a special case. Our new student is going to be with us only until he’s able to pass off courses to prove his degree-" He shook his head as though this is the weirdest thing he's ever heard. 

The other students in the class were all pretty confused as well, but (Y/n) just wondered where the student would have gotten a degree they'd have to prove at an accredited school. 

"Everyone please make our new student feel welcome." 

The dean entered the room, followed by a relaxed looking person, wearing pink slippers over slouching socks, loose sports shorts, and a somewhat baggy, well loved hoodie. 

It took a moment, but as the pair stopped and faced the room, the new student blinked, taking in his new environment, grin as relaxed as the rest of his body, hands stuffed in his pockets, the white lights in the darkness of his eye sockets perusing the space, and (Y/n) realized that they were a skeleton monster. 

She felt her jaw go slack and her lips part, her heart starting to race in her chest. 

The dean was reminding them all that harassment and anti monster behavior wouldn't be tolerated, but she couldn't focus on his words, too focused on the monster himself. 

He was the first monster to ever attend the school, though it wasn't strange, as monsters had only been on the surface for about a year and a half, and most of that time was consumed by all the ridiculous government red tape and regulations, trying to decide where they belonged in the world and what rules and rights they deserved. 

So it wasn't strange that he was also the first monster that she'd seen in person. 

Her reaction was a bit odd, though. 

She subtly checked her pulse- not having a heart attack… but it was definitely pounding inside her ribs like it was trying to get out, only- she wasn’t afraid. 

Instead of fear, she felt… a strong sense of attraction.

He was now studying the class, looking at every person individually as though he were looking for something. His eyelights landed on her, pausing before continuing through the rest of the class. 

He was dismissed to sit down, and he started through the room, (Y/n)'s heart skipping a beat as she realized that he was headed her general direction. 

"Hey," one of the more 'outgoing' students reached their hand out to him, making him stop moving forward. "My name's Cody. Welcome." 

"sans. sans the skeleton." 

He reached out and a whoopee cushion sounded as they shook hands, but (Y/n) was stuck on how wonderful his voice was. Deep and low… It sent shivers down her spine and through her belly. 

.

Cody was a nice person, not a bigot in any way, not hating anyone for who or what they were, but he did like to collect friends, taking pride more in the diversity of his collection and always 'knowing a guy' to be the friend broker, than in how much fun they had together. 

It only took Sans two parties to figure out exactly where he fit into the group. 

He didn't like being the trophy monster friend, or 'the guy that could…' if anyone ever needed anything that he'd be able to help with. 

He was glad when the science class changed subjects so that he could change seats, the ‘study groups’ changing into ‘lab partners’. 

"Sans can be our lab partner," Cody called out, trying to claim him again, but the professor disagreed. 

"Cody, let other people have the chance to hang out with him. Now, looking over my roster, it looks like…" 

He checked through the names, finding only one without a name or line by it as Sans stood by. 

"The only person without a lab partner for the next section is… (Y/n)-" He looked up to see her quietly off by herself at a table. "Oh, yes, (Y/n). You two will be partners." 

Sans walked toward his new seat and saw his new partner, giving his standard lazy grin. "hey." 

"H-hi." Her voice was quiet, tinged in nervousness, but not shy, just soft. 

He thought it was cute. 

.

They got along well, though most of the reactions Sans got from her were in the form of soft noises; laughing at his jokes, hums of agreement or disagreement, a humorous click of her tongue with a smile when she thought he was being a dork. 

Sans, though not usually much of a talker, found he liked her voice and wanted to hear it more from the few times she'd spoken, and talked to her a lot, hoping to get her to respond verbally. 

"hey, (y/n)," he started, pausing, but she only hummed in question. He looked at the set of things in front of her. "can ya hand me a pipette?" 

She reached out, taking a pipette and offering it to where he was sitting at her side. 

Sans took it in his phalanges, but froze, his soul leaping to his nonexistent throat as the side of his hand touched her, for the first time. 

It was like a jolt of electricity shot through every bone of his body from that one contact. He couldn't pull his wide sockets from her, his soul thrumming against his ribs as he watched a coy expression of embarrassment flash on her face as she looked in the opposite direction of him. 

It was her. 

It was her! 

She was his soulmate! 

He'd felt his soulmate when he'd arrived at the class that first day, and had discretely been trying to figure out who it was since, spending a bit of time around every person in the class he could for the last few months. 

It was her! 

(Y/n)! 

He'd noticed her, thought she was cute, but pushed that thought out, not wanting to have a hang up on her if he found his soulmate was someone else. 

But it was her! 

He felt his grin get a bit goofy as his eyelights undoubtedly flashed to hearts. 

(Y/n)... Such a sweet name… 

She was a really sweet person, too… 

The bell chimed and she looked up to the clock before gathering her stuff and starting to clean up. 

"Sans?" She asked and he was glad she wasn't looking directly at him at that moment, since his eyelights flashed hearts again at her voice saying his name. But then she looked up and met his sockets and he felt like he'd been being deprived of something necessary. "Are you ok?" She asked, her face showing her concern. 

Stars- she was so sweet- so perfect and beautiful- 

Sans cleared his throat. "y-yeah. i'm good…" 

She gave him a soft smile and stood, pulling her bag over her shoulder. "See you tomorrow, then." 

"yeah," he answered, watching her go. 

.

Sans was beyond ecstatic, and could hardly keep his mind on his tasks. 

When he sat next to her again, where he'd only sent puns and jokes before, he was now putting out pickup lines. 

"(y/n), come on, baby, light my fire," Sans' low voice encouraged. 

(Y/n)'s eyes shot to him, a bit wide. 

...until she saw he had the bunsen burner out and the lighter was on the other side of her. 

"Oh- I- haha, ok," she answered, lighting the burner. 

Sans studied her for a moment. 

She seemed immune to his flirting. 

Or… 

Maybe she couldn't tell? Maybe she thought he was still just telling jokes… 

"Sans-" 

God he loved the way she said his name. 

"What is it you're hoping will happen by heating it up?" 

"huh?" It took a moment for him to realize she meant the things they were doing for class. He chose to flip it to suit his desires. "hopin' to get a positive _reaction,_ but ya just can't seem to look at me long enough for me to gage my results." 

(Y/n) looked up at him from the paper she was taking notes on, her eyes widening again. 

He didn't look away. 

Her lips parted, but she didn't know what to say, so they closed again. 

"i could always run another experiment, and see what your lips taste like," he told her, giving a charming grin. 

"I- uh…" (Y/n) bit her lip, then one side lifted up. "That sounds like it belongs in private study." 

Sans scooted a bit closer. "i could definitely get into some _private_ study." His grin widened as he winked and his sockets lidded as his voice grew huskier, suggestive. 

His voice was so deep, rumbling through the air and through her chest, making her body react. 

They spent the rest of the month that way, getting close, Sans flirting nonstop, (Y/n) laughing, teasing and flirting back. 

Finally, Sans couldn't take it anymore. He caught her wrist after class one day, guiding her to the edge of the classroom like they were leaving, and having her wait as everyone else left, the professor heading out for his free period to get some lunch. 

(Y/n) looked back at him in question after they both watched the last people leave and the door close after them. 

He grinned, seeming eager for something as he moved in closer. 

He took her hand and ran his phalanges over it, bringing it up to his teeth, nuzzling it. "you, uh, you ok with this?" 

"With kissing?" She asked, nearly chuckling. "I don't know how it was in the Underground, but around here, usually by the time you become an adult you've had a kiss, though it does depend on the person and their preferences. Are _you_ ok with kissing?"

Sans chuckled and pulled her against him in answer, his teeth meeting her lips. 

His teeth seemed to act in place of his lips, moving slightly as they kissed, pressing harder against her as the kiss grew hotter. 

She felt his teeth part, and a tongue touched her lips, asking entrance that she quickly granted. 

A moan left her, and (Y/n)’s hands found their way to his hoodie, clenching around the faded, though still soft, fabric. 

Heavy breathing and small noises filled the air around them as Sans found a wall, leaning (Y/n) against it as his hands pulled her closer, his body pressed tight to her. 

His hands slid down her ribs to her hips, trailing around and squeezing her sides through her shirt, then edging his phalanges under the hem. 

“you’re so _soft_ ,” he groaned against her mouth. “shit- i can’t wait to touch ya…” 

A needy gasp left (Y/n) at his words and touches, her hands returning the favor and sliding down his sternum to navigate their way under his jacket, feeling his solid ribs and clavicles under her hands as she slid them back up. 

“mmmmm…” He was groaning desperately, grinding something warm and stiff against her as his hands explored around her lower back, squeezing her sides and hips as they moved. 

“mmm, want ya so bad, (y/n),” he murmured against her between tangling his tongue with hers. 

(Y/n) let out a gasp, pulling in enough air to answer, “I want you, too, Sans-” 

Fuck, he was going to come in his shorts if her sweet, hungry voice said his name like that again… 

“Have for a while…” 

“yeah?” He asked. 

She nodded with a hum, her hands trailing up over his clavicles and to his shoulders, one running over the base of his skull, the other letting her fingers trail patterns over his exposed vertebrae. 

“stars, you’re so sexy,” he told her, his hands landing above her waist, his phalange tips digging in as he pushed as close as possible, grinding against her again. 

“You, too,” she answered, nipping at his jaw. 

Sans growled, one hand going to a thigh and pulling it up around him, pressing and grinding as hard as he could to the growing wet spot between her thighs, making her whimper. His other hand slid up her shirt and began massaging her breast through her bra. 

“I hope this is ok,” she murmured against his vertebrae, licking and nipping at them as she made her way down. “I’ve never been with a monster before- I don’t know if we have different sensitive spots or what…” 

“it’s good- ungh- you’re drivin’ me fuckin’ nuts, babe,” he told her, and a pleased moan left her as he let his skull fall back, giving her more space to work as he kept pressing and grinding against her, his hands groping and squeezing her breast and thigh. 

(Y/n) could feel her panties starting to stick to her, and was looking forward to getting them off, knowing that there was only more fun to be had. 

“that why you’re doin’ this?” Sans asked, groaning as he pressed his aching cock against her heat again. 

“Huh?” She asked, her head coming up to look into his sockets. “Is what why?” 

“bein’ with a monster. the new territory, the novelty,” he suggested, still looking very into it as he leaned in to kiss her again. “got a monster fetish?” He teased. 

(Y/n) brought her hand up to block him, and he let his tongue slide out, licking around her fingers. 

She ignored it, landing one fingertip against the point of his chin. “Is that why _you’re_ doing this? Just… for the novelty?” 

Sans stopped, pulling back, his eyelights taking in the hurt she was trying to hide. 

“You have a human fetish or something?” She asked, her voice nearly hiding the waver of sadness. 

“(y/n), i-” 

She pushed him back, disengaging his body from hers and freeing herself from his hands. “That’s not what I’m doing.” 

She was trying to stop herself from crying- his soul hurt; he didn’t want her to be unhappy- 

“I-if that’s what you’re after- I’m sorry, but you’ll have to f-find someone else.” 

(Y/n) turned and left, ducking and dodging away when he tried to reach out to her. 

Sans’ soul throbbed and stuttered painfully in his chest, and his hand went to his sternum, rubbing at the bone covering it. He could only watch her as she hurried out through the door, still stunned. 

What- 

What just happened? 

What did he do?

His soulmate had just run off crying- 

Oh stars- 

_What did he do?!_

. 

Sans had been propositioned by some of the other people in the school over the last few months, people who just wanted to try out being with a monster. There may have been a time when he would have accepted- but he’d felt his soulmate somewhere close by, and he only wanted them, now. 

When he’d found out it was (Y/n), he’d only wanted to see if she was in it for the same reasons, mentally begging fate not to be that cruel- it would break his soul if he got to have her and then she left, him finding out after that she’d only wanted the experience… 

Having a human soulmate was so problematic… partially because they couldn’t feel their souls, so they couldn’t feel the pull when they found their soulmate… partially because they had the ability to ignore their souls… 

But it made sense now why he’d always been more attracted to humans and human characters in the anime Alphys had shown them… 

Fuck-

He hit his hand against his skull, again. 

Fuck! 

His hand crashed onto the table in front of him. 

(Y/n)... 

He could feel his soul crying out for her. Begging him to go to her. Straining to catch just a wisp of her essence. 

The door opened, drawing his attention, and another group of students entered the science classroom. 

His eyelights trailed over to the spot of the wall he’d had her, his soul aching behind his ribs. 

He looked up as the door opened again, and followed (Y/n) as she walked to their table and sat down, pulling out all of her material and readying herself for class. 

“(y/n),” he started, but she put a hand up, stopping him. 

“Let’s just get our work done,” she suggested. 

.

Stars, it hurt. 

His soul ached until he couldn’t sleep, thrumming loudly and calling out for (Y/n), only for her soul to give no call in response. 

It was worse when they were in class, literally within touching distance- only she made sure to never touch him. Not even on accident. 

What hurt worse was that she wasn’t even rude or confrontational about it. 

She’d told him that it was fine if they wanted different things, but that she wasn't interested. 

And then she was just polite to him. 

_Polite_ , like she’d be to a stranger, not like she'd be to someone she’d been flirting with for a month, and definitely not like she'd be to the one who was her soulmate. 

He was her soulmate - _her soulmate!_ \- and fuck the stars, she _couldn’t feel it!_

He’d never been in this much pain, the only thing close was when he’d lost Paps, over and over again before Frisk had finally stopped resetting and freed them. 

Sans lost interest in things, everything, slowly, one by one. 

He started wearing his pajamas to school, barely finding a shirt that didn’t have ketchup or other suspect stains on it before shortcutting there. 

His only reason for going now was to sit next to (Y/n) in their class together, getting that short time next to her to try to stop his soul from hurting. 

She wouldn’t talk to him about what had happened. Any time he tried, she suddenly had somewhere to go, something to do. 

He stopped trying. 

The only thing stopping him from wanting to dust was the moments he got to spend next to her, and his brother. 

. 

(Y/n) walked down the hall, eyes toward the ground, minding her own business, hearing the hushed whispers of other students in the enclosed space. 

“EXCUSE ME, HUMAN.”

She looked up, and up, and up, to see a very tall skeleton monster holding a large, closed tupperware container. 

“How can I help you?” She asked. 

“I’M LOOKING FOR MY BROTHER, HE’S BEEN VERY LETHARGIC LATELY- MORE THAN HIS USUAL LAZINESS- AND I SUSPECT THAT HE IS UPSET ABOUT SOMETHING, SO- I THOUGHT I’D BRING HIM SOME CHEER UP SPAGHETTI FOR LUNCH!” The tall skeleton’s skull changed from concerned to determined in an instant. “ONLY- ONLY I CAN’T FIND HIM…” 

(Y/n) couldn’t hold back the smile he’d caused. He seemed to have an infectious sort of happiness, even when he was worried. “So, your brother is a student here?” She asked, pretty sure she knew who it was, but not wanting to jump to conclusions in case there was another monster around she just hadn’t seen. 

“OH, YES- FOR A TIME ANYWAY- A TIME THAT KEEPS GETTING LONGER AND LONGER THE LESS TIME HE SPENDS ON HIS GOAL AND INSTEAD ON MOPING…” The concern was back in his loud voice. 

“Is your brother, by chance, named Sans?” She asked. It really seemed to fit- she couldn’t think of anyone else in that type of situation… 

“YES!” The tall skelton exclaimed joyfully. “DO YOU KNOW HIM, THEN?!” 

“He’s actually in my next class. Would you like me to give him the spaghetti?” She asked. 

“UM…” He seemed to consider it deeply. “THAT IS A VERY CONSIDERATE OFFER, HUMAN, BUT- I THINK I SHOULD DELIVER IT MYSELF!” 

(Y/n) chuckled. “Certainly. I’ll show you where it is, then,” she told him, gesturing for him to follow. 

Sans laid his head on the table, eyelights staring unseeingly off into the distance. 

(Y/n)’s voice echoed down the hall, into the classroom- a laugh- 

His soul twisted. 

Who was making her laugh like that? So genuinely and happily? 

She entered the room and quietly made her way to their table. 

“Sans-” 

His soul reached out to hers, begging for a hint of recognition. 

“You have a visitor.” 

She wasn’t even looking at him. 

He pulled his eyelights away from her and looked to see his brother waving cheerfully from the doorway. 

Sans slumped from his chair and shuffled over, stepping into the hall. 

“HELLO, BROTHER!” 

“hey, bro…” 

“SO, YOU KNOW THAT HUMAN? SHE’S VERY NICE!” 

Sans’ phalanges gripped his shirt over his soul as another wave of pain hit. 

“B-BROTHER… Sans… Are You Alright?” Papyrus asked, his concern obvious. 

“she’s- she’s my soulmate, paps,” he blurted, unable to say anything else. 

“SHE IS?! THAT’S WONDERFUL!!” Papyrus exclaimed, holding the plastic bowl of spaghetti to his ribcage and gazing out into the distance. “I’LL HELP PLAN YOUR BONDING CEREMONY- WAIT. IF YOU FOUND YOUR SOULMATE… THIS IS A HAPPY OCCASION, WHY ARE YOU SO GLOOMY?” 

“because she hates me, paps…” Sans murmured. 

“OF COURSE SHE DOESN’T; YOU’RE SOULMATES!” Papyrus told him as though it was the most obvious thing in the world. 

“she does, paps… i said something stupid. it didn’t seem stupid at the time, but… it upset her…” 

“WAS IT ONE OF YOUR INTOLERABLE PUNS?” Papyrus asked. “EVEN THOSE ARE NO MATCH FOR A SOULMATE BOND-” 

“she’s human, paps, she can’t feel it.” Papyrus’ expression fell at that. “so, now she hates me.” 

“YOU- YOU NEED TO TALK TO HER-” 

“she won’t talk to me,” Sans interrupted, his soul-ache obvious in his voice. 

“YOU- You’ve Tried?” 

Sans nodded. 

Papyrus looked back through the doorway thoughtfully, letting his gaze rest on his new human friend for a moment. 

“MAYBE YOU JUST NEED A LITTLE HELP FROM THE GREAT PAPYRUS,” he suggested. 

“i wish that’d help, bro-” 

“YOU’LL NEVER KNOW UNTIL YOU TRY. NO LAZING OUT OF THIS ONE! NOT WHILE YOUR FUTURE WITH YOUR SOULMATE IS ON THE LINE!” With that, Papyrus turned with a swish of his scarf over his shoulder and started off down the hall. 

Sans stood there for a moment, his phalanges still clenched in his shirt. 

. 

(Y/n) stretched her arms over her head as she made her way along one of the outdoor paths across campus, letting them fall back to her sides. 

She felt melancholy lately. Like she was missing something or was supposed to be doing something, but had no idea what. 

The feeling seemed to start shortly after she'd kissed Sans in the classroom, but… there was no reason to be upset about that, right? 

They just wanted different things! 

There was nothing wrong with wanting to be with someone without a relationship, just like there was nothing wrong with wanting a relationship if you were going to be with someone. Different strokes for different folks and all that. 

"HUMAN!" A boisterous voice called out, startling (Y/n) from her reverie. "HUMAN!" The voice got closer, and she looked up to see Sans' brother, Paps, he'd called him when he'd talked about him. 

"Hello," she greeted as he got close to her. 

"HELLO! I'M GLAD I COULD SEE YOU AGAIN!" He genuinely looked happy about it, and it made her reflect his smile. 

"Good to see you, too," she told him. 

"IT'S ALWAYS A GOOD DAY TO SEE THE GREAT PAPYRUS!" He declared, and she chuckled softly. "ANYWAY- Ahem, Anyway- I Was Wondering If I Could Ask For Your Help With Something!" 

That surprised her, as they'd only met once before. Surely he knew many other people that would love to help him, and would be better at it than her. But she couldn't refuse this sweet bean. "Wh- what can I help you with?" 

"Well, There Is An Event Coming Up, A Bonding Engagement, And I Want To Host A Party For It! There Will Be Humans There, And As The Greatest Host, I Want To Make Sure That There Will Be Food That Will Fit Their Palates! Though I Can't Imagine That Anyone Could Find Fault With The Great Papyrus' Cooking!" He told her. 

She was a bit envious of his blaring confidence. "I, um, I'll do what I can to help," she told him. 

"That's Wonderful! Thank You, Human (Y/n)!" He put out his gloved hand, holding a piece of paper to her. 

(Y/n) took it, looking at it in question to see an address. 

"I'll See You At This Address Tonight For A Planning Meeting! Seven! Don't Be Late!" He called over his shoulder as he walked away. 

"But- I-!" (Y/n) tried to object, but he was waving happily at her, calling that he was excited for that night, striding away quicker than she'd ever hope to catch up with. 

She sighed, looking down at the paper. 

It was probably his home, and while she didn't have a problem meeting him, it was also probably Sans' home… 

But she couldn't just not show up after she said she would… And she didn't have a way to contact him, other than talking to Sans. 

.

The address turned out to be for a house in the section of town that the monsters had been allocated to, and it took a while to get there on the bus. 

When she knocked on the door, Papyrus answered, extremely excited to see her. 

He ushered her in, and directed her to the kitchen where some papers and ingredients were hanging around on the counter. It was a very nice and clean kitchen, fully outfitted with appliances, in good looking condition. 

They were the only two there, so (Y/n) felt it easy to relax. 

They talked about the kind of things that Papyrus had planned, (Y/n) agreeing that puzzles were definitely a fun idea, seeming extra happy and commenting on how glad he was that they'd get along when she told him she also liked puzzles, and putting in sometimes when he talked about putting things together that didn't seem like they belonged together, like a dessert spaghetti with ice cream and chocolate sauce, but with regular noodles. 

They made a few things to taste, (Y/n) laughing at Papyrus' anecdotes as they cooked. 

When they got to the end to taste it, a whole plate of each option was sitting on the counter, waiting for appraisal. 

They tasted, writing down their decisions and discussing how they would fair, but when they'd finished with the last plate, Papyrus looked around, as though something was missing. 

"Oh! How Stupid Of Me! I Forgot One Of The Most Important Things! I'm So Sorry, Human (Y/n)! I Must Have Left It At Undyne's! I'll Go Get It And Be Back!" 

"Sh-should I come with you?" (Y/n) asked, figuring that it would probably be weird to leave a virtual stranger alone in your house. 

"No, No, It's Fine! I'll Be Ok, Grabbing It Myself! I Am An Adult After All!" Papyrus assured, heading to the door, a whirlwind of movement and speech as he left. 

It was quiet after the door closed, everything settling back down. 

(Y/n) waited patiently, politely not touching or messing with anything. 

It was about five minutes later that she looked over the snacks, eating another of the ones that were her favorite, putting another positive mark on them. 

The door opened and closed in the other room, and (Y/n) felt glad that it really hadn't taken too long for Papyrus to get back. 

But the skeleton that walked into the kitchen wasn't the taller, more excitable one she'd been expecting; it was his shorter, slouchier brother. 


	2. Where all the smut is

**Summary for the Chapter:**

> Sexy times here *arrow pointing down*

**Notes for the Chapter:**

> You get to find out just how smart and good at getting people to do things they don't realize Papyrus is...

Sans walked into the kitchen, freezing in the doorway as he felt his soul leap, its cries for its mate getting louder. 

He dragged his eyes from the floor and saw (Y/n) looking back at him from where she was leaning on the counter. 

His brother's message telling him to get his sorry coccyx home and that he had something special waiting for him in the kitchen made sense now. 

"(y/n)," his voice was broken, even to his auditory canal. 

She straightened from the counter, and the pull of his soul made him appear directly in front of her, his hands lifting, hovering, wanting to touch her, but afraid she'd run. 

"Sans-" She sounded hesitant, but hearing his soulmate say his name, when he was already at the edge of tipsy, broke his patience. 

Sans pulled her against him, one arm around her back, one hand tangling his phalanges in her hair as he buried his nasal ridge in her neck. 

"stars, please," he begged, his arms tightening around her. " _please_ \- don't go, my soul's beggin' ya, (y/n)." 

"Y- what? Your what?" She asked in confusion, not even trying to push away from him. 

"my soul is beggin' ya not to leave- stars," he squeezed her against him, "it can't stand bein' away from ya…" 

"Is that your pitch this time?" (Y/n) asked a little stiffly. 

Sans pulled back, his eyelights going to meet her gaze. "huh?" 

"Dropping the whole 'novelty' thing?" She asked, her voice edged with a hint of bitter feelings. "I can't believe you dragged your sweet, innocent brother into your fucked up plan to get laid! How low can you get?!"

A flash of anger washed through him, and he held her away by her shoulders. “shit- forget novelty- (y/n), i was just tryin’ to find out if ya were only interested in me ‘cause i’m a monster! and i didn't drag paps into anything! anything he did he did on his own!"

“'Cause you're a monster…? Why in the hell would you think that?” She demanded, her hands going to his shoulders, pushing away a bit as she stared right back into his eyelights. 

“i- i just had to know! imagine; finding your soulmate, and they only want to be with ya because you’re some type they’ve never been with before! imagine how stars forsaken it would feel if the _one person in all the universe made for ya_ only wanted a quick round of fun!” The desperation in his low voice held (Y/n)’s attention, even as his eyelights started to drift down. “imagine, ya find the one person that’s perfectly yours, and they only… want ya as a conquest…” 

“Is that what happened to you?” His eyelights flicked back up to her face at her soft voice. “Did… did you find your soulmate- and… and they only wanted to- have a one night stand?” She tried to be gentle, not wanting to make him fully relive whatever pain he’d gone through. 

“(y/n)...” Sans hesitated, unsure how to continue for a moment. “ya- y’know, there _have_ been a bunch of people tryin’ to get into my pants, thinkin’ it’ll be interesting to try bein’ with a monster, but my soulmate never did that. she actually got mad when i suggested it.” 

(Y/n) bit her lip to keep from chuckling. “Wow, you really have a habit of putting your tarsals to your mandible, huh?” 

Sans’ phalanges cupped her cheek, tilting her face to him as he leaned forward. “my soul’s been on the edge of shattering since she ran- left me there alone to feel how stupid i was…” 

His skull touched her forehead, sockets closing as he nuzzled her for a moment before shifting and pressing his teeth to her lips. 

(Y/n) reacted instinctively, her lips parted, her tongue meeting his as he took it deeper, pressing her tight against him. 

A needy sound hummed from Sans, and he felt the counter giving resistance from behind (Y/n), one hand dropping down her side to massage her from hip to thigh. 

(Y/n) groaned, feeling his other hand starting to work over her breast, groping and squeezing it as he searched for the bump that had made her whine in excitement last time. His teeth moved down her throat, nuzzling, then leaving a trail of nips and licks in lieu of kisses. 

His hand slid down her leg behind her knee and wrapped it around his pelvis, then trailed back up, sliding under her shirt as it moved to join the other in giving attention to her breasts, groping and massaging, one under her shirt, the other over, both pushing them toward his skull. Sans nipped and licked at her clavicle, grinding into her, something stiff and warm again pressing into the wet spot between her thighs. 

(Y/n) moaned, her head falling back as he pressed against her. She blinked and dragged her eyes open to look at him. “Sans- wh- uungh- what a-bout your- oh, y-yeah, nnn- soulmate,” she gasped, arching against him as he ground into her. “D’you think she’ll be ok with- this?” 

Sans nipped his way back up her throat, dragging his tongue over a particularly sensitive spot. “‘s you,” he told her. “you’re my soulmate, (y/n). stars- the things i wanna do to ya… wanna show ya just how happy i can make ya, take care of ya- mmmmmm,” he let out a low, lewd groan, “feel how perfect ya are for me… stars- i bet ya feel like heaven…” 

(Y/n)’s lashes fluttered as she looked at him. “M- me?” 

He hummed in agreement. 

“A- and _I’m_ your soulmate?” She asked, stunned. 

“our whole lives, (y/n), even if we just found each other,” he told her, not stopping his attention to her body. 

She didn’t know what to say. She had a hard time thinking what to say, too, what with Sans’ mouth and hands on her and his body pressed against her. 

“mmmmm, (y/n), babe- mmm- i wanna take ya to my room,” he confessed, grinding against her. “lay ya down, and make ya _scream_ my name,” he growled. 

More wetness flooded her panties at the rumble near her ear, and a whimper escaped her. 

Sans growled again, grinding his bulge into the hot space between her thighs. “mmmmnngh- ya want that, sweetheart?” He asked, starting to rub against her in a slow rhythm. 

His phalanges found the bumps of her nipples under her clothing and pinched, giving a bit of a tug. The keening cry she let out drew another rough growl from him, and his hands left her breasts to grip her hips, lifting her to the counter and almost laying her back. 

“shit-” he gasped, “(y/n), sweetheart, i need ya so bad…” He was about to drop his pants right there in the kitchen, forgetting where he even was, and how pissed off Paps would be if he fucked his soulmate senseless on the counter. 

(Y/n) arched to Sans again, her hands clenching in his jacket and tugging him closer against her. “Sans,” she gasped. “Yes- ah, god, yes, please…” 

Sans chuckled into her neck. “didn’t think i’d get ya beggin’ for me so soon,” he teased. 

He lifted her from the counter and held her hand, leading her up the stairs to his room. 

(Y/n) followed, looking around the room that was revealed when he opened the door. 

It was a bit messy, papers and books on the desk pushed into the corner and on the floor around it, dirty clothes piles here and there, a bare mattress on the bed frame with dirty sheets crumpled up into a ball, a set of clean sheets haphazardly folded on the floor next to the bed, half under it. 

Sans cursed and went to the bed, taking the clean sheets and tossing them around until he found the fitted one, quickly stretching the sheet onto the bed before tossing the pillows onto it as well. 

“sorry, i, uh- wouldn’t want our first time to be on a bare, scratchy mattress…” He rubbed at the back of his skull. 

(Y/n)’s lips quirked up before she schooled her expression back to normal. “You’re right Sans… we’re soulmates-” Sans’ soul soared to hear her say it- “we wouldn’t want our first time to be…” She trailed off, gesturing around his room. “Subpar… we want it to be perfect! Maybe we should wait, get a really nice suite, maybe plan a whole long date to get us in the mood first,” she suggested. 

Sans looked nervous, his eyelights darting around the room, to her, to his bed, then back to her. “ya- ya serious, babe?” He asked, his voice wavering with nerves. He'd waited so long, mostly caused by him being a fucking idiot, but he knew it would be difficult to gather enough patience to plan out and last however long it would take to get to the end of the date so he could have his soulmate to himself like this. 

“Nah- we don’t need that stuff- let’s do it now!” She answered, laughing at her joke. 

“oh, thank the stars,” Sans sighed in relief, pulling her close and pressing his teeth to her lips again as he led her to the bed. 

(Y/n) automatically lifted her arms as Sans pulled her shirt over her head, pausing to look her over before going back to her lips. 

"shit," he breathed. "you're so beautiful…" 

Sans' phalanges ghosted over her bare skin, making goosebumps raise after them, and (Y/n) felt the clean sheets under her back as he laid her down. 

He knelt between her thighs, her hips pulled up so her ass rested on his femurs, grinding hard against her, groaning against her lips as their tongues tangled. 

(Y/n) ran her fingers over him, one hand moving over his chest, sliding around his ribs to rub at his spine while her other fingers traced and explored the exposed vertebrae of his neck. 

She pushed at his jacket, and his arms flailed a little behind him as he tried to rid himself of the thing, only remembering when it was flying to the floor that she had something else stopping him from touching her bare skin and sent his hands on a search for the hooks to get it out of the way. He found them, but fumbled a bit before managing to separate them, dragging the clothing down her arms, his eyelights staying on her breasts the whole time. 

He couldn't coordinate it to throw the contraption in his hand, instead letting it drop and fall to the floor as he softly cursed. 

He dove towards her chest, his phalanges cupping and massaging her breasts as his skull planted between them, turning from side to side to take turns with each, licking and nipping, gently tugging her nipples with his teeth. 

(Y/n) gasped and moaned under him, her back lifting in an attempt to get more attention to her breasts, her hips arching to grind against the stiff bulge pressing hard against her. 

She let her hands run over his back, pulling his shirt up to let them run over his bare ribs and spinal column. Her nails caught on his bones as her fingers curled, scratching over them as she arched up. 

Sans let out a growl as he straightened, slipping out of his shirt, and dragged his hands down to the band of her pants, catching her underwear as well when he quickly dragged them from her, pulling her legs straight into the air instead of letting her have any distance from him. 

Sans laid her legs around his pelvis again and started gently rubbing up and down her thighs. "ya look so perfect all laid out here for me," he told her. 

(Y/n) felt herself getting more excited as he moved, one hand trailing up between her thighs, his thumb skirting over the outer lips of her pussy, brushing against it and stroking until it had made its way in to stroke along her from opening to clit. 

His other hand slid up her body until it was back to her breast, massaging and playing with her nipple, pinching, twisting, and tugging, taking in every expression she gave at his ministrations. 

(Y/n) could feel Sans stroking her pubic symphysis, rubbing over it, the rest of his hand splayed out along her thigh. It was something that she'd never felt before, but it was definitely good. Trust a skeleton to be able to make her bones give her pleasure. 

"(y/n), you're so warm here- around my thumb," he groaned as he sank the phalange into her. "oh, shiiit… so tight… i'm goin' to have to open ya up…" 

Sans kept his hand moving on her breast, massaging and groping it, phalanges playing with the nipple, still running his thumb over her, dipping into her hole every few strokes. 

She jerked and let out a sudden, loud noise as he rubbed over her clit, and he paused, a heavy breath blowing over her ribs. 

"(y/n), move your arm, babe," he told her. She shook her head under it, where she'd hidden in embarrassment. "c'mon, babe, please? i wanna hear how good i'm makin' ya feel," he told her, softly touching her clit. 

She managed to pull her arm away, her brow furrowed and eyes clenched closed as she pointed her face away. 

“you’re so damn gorgeous, (y/n),” he told her, starting to nip at her ribs as his thumb started rubbing over her again, dipping in and circling her clit. “all those sounds you’re makin’ are makin’ me want ya even more, sweetheart,” he groaned. 

He continued his handiwork, drinking in the delicious noises she was making, taking it slow and soft until she was right at the edge, when he circled her clit with his thumb to push her over, his jaw clenching as he growled. His thumb slipped down to sink into her over and over, searching for that magical spot and rubbing it as he worked her through her orgasm. The cry of pure pleasure she gave as she squeezed around his phalange redoubled his growl, and he bit her ribs, his teeth pressing hard against flesh and bone. 

As tight as his shorts were, he felt them get even wetter and stickier as the bite only made her cry out again as she arched up to him. 

(Y/n) gasped his name as her hips squirmed, her hands grabbing for him and finding his shoulder and hand. 

Sans traded his thumb for his index and middle phalange, carefully rubbing over that sweet spot on the way in and scissoring them apart on the way out. “that’s it, babe, keep comin’ for me, squeeze my fingers like you’re tryin’ to choke ‘em… ‘cause i want ya to choke my cock with this sweet lil pussy next.” 

(Y/n) squirmed as a shiver of heat rolled through her at his dirty talk. She was getting close again already, his clever phalanges teasing just the right spots inside her as his other hand treated her breasts the perfect way to intensify every touch. 

Sans groaned as he felt her come, squeezing at him again. Stars, he wanted her so bad. She whined out his name, begging him not to stop as he focused in on her sweet spot, and he couldn’t hold back anymore, pulling completely away from her to kneel between her thighs again. The whine of betrayal at suddenly losing his boney fingers made him growl and fumble a little as he fought his shorts to his femurs, letting his cock spring free. 

(Y/n) looked at how the blue member proudly jutted into the air, and felt herself clench in desire, even though she mentally felt a bit intimidated. 

He was a bit… big. 

Not so big that she worried about internal hemorrhaging, but big enough that she was concerned that he would be abusing her cervix beyond what it may be able to take. 

Sans pulled her up onto his femurs again, pulling one thigh over his shoulder and wrapping his arm around to place his hand on her hip. His other hand took his length in hand and guided it, rubbing it up and down her crease spreading his precum over her slit. His cock gave a twitch at the sight he had, his eyelights unable to move away for a moment. 

“ya want this?” He asked. 

“Mmm- mmhm,” (Y/n) moaned in response.

“ya gonna come hard for me when i get this thick, hot cock in ya?” He asked, circling her clit with the head. 

“Yeah,” she moaned to him. 

Sans lined the head up with her opening and slowly started pushing in, his breath hissing out at the hot press of her tight walls. He let out a groan, his skull falling back as he slowly sank in. 

He was going so slow it was like a prolonged torture, pressing himself into her, but he had to go slow; it wouldn’t do to injure his soulmate during the initial thrust of their first time together. 

He planned to have many, many more rounds with her before the sun came up. He was going to fuck her until she couldn’t think straight- she was going to have to ice her pussy when he was done with her. 

Of course, she’d be a boneless heap, but he’d gladly help her; lovingly holding an icepack to her poor, swollen, abused mound, maybe grinding it against her just the slightest bit to get a few more orgasms out of her. 

Sans jerked at the thought, going a little faster than he’d intended and making her gasp. “oh, f- fuckin’ _stars,_ sw- sweetheart… ya feel s’good…” He let out a needy groan as he slid the rest of the way home, _finally_ hilting. 

(Y/n) was trying to catch her breath, the feel of her channel stretching to accommodate him already making her more aware of how good he felt inside her. 

Sans started to pull out, still going slowly, his breath coming in long gasps and groans. 

(Y/n) tried to hold still, not wanting to jerk her hips and possibly hurt either of them, but her body was giving its protest of his cock leaving it, rocking and twitching as it tried to get him back inside. 

He pushed in a little faster this time, his skull bowing forward as his breaths got faster and faster, coming in a rough pant as he cursed and praised her simultaneously. He hilted again, both of them gasping for air and trying to stay calm as he took a moment to let her adjust. 

“ya ok, babe?” He asked breathlessly.

“Y-yeah,” she panted. 

“then, let’s see how much your pussy can take, sweetheart,” he groaned, pulling his cock out and shoving it back inside her. 

(Y/n) cried out as Sans gave quick, rough thrusts, his hands tightening on her hips as he pounded into her. 

“stars, sweetheart, imma find a constellation and name it after ya- shit- oh shit, ya feel so damn _good!_ dunno how you’re doin’ it-” Sans ranted, grunts and groans leaving him as he plunged into her again and again, “must be b’cause- b’cause you’re- you’re the- oh- oh stars- shit- ungh-” His pelvis faltered as she arched and tried to meet his thrusts, but he managed to regain his rhythm and keep up his pace. “you’re the only one i- belong with-!” 

(Y/n) felt cries and moans leaving her, lewd noises that she’d normally be embarrassed by, but the way he was pounding into her was numbing her inhibitions and making her body wantonly beg for more. 

“shit- oh, babe, i feel ya gettin’ close there- c’mon. c’mon and- come for me,” Sans groaned, the slap of his pelvis against her soft flesh filling the space around them. _“come for me, sweetheart, come for your_ **_mate_ ** _,”_ he growled, his deep voice rumbling through her whole body. And she did. 

Stars filled her mind- not imaginary fireworks, but darkness filled with pinpricks of light, as her mind blanked and she came so hard she felt the pull against her muscles as Sans had a bit tougher time pulling out. 

“fuck- f- yes- oh, fu- ck-” Sans choked on his words as he fought to keep going through the tight convulsions of her orgasm. “oh, sweetheart- _tha’feelss’good_ \- yes- stars, yes-! f- fucking- _shit_!” He crowed as he came, his pelvis slamming into her jerkily as he filled her with his heated seed. 

(Y/n) nearly screamed, crying out his name as her orgasm held on through his, waves of pleasure rippling through her in time to his thrusts. 

Sans slowed, giving soft, gentle thrusts, his hands still gripping her hips as he watched his cum drip out of her with each push in. 

He finally stopped, pulling out and laying her hips on the bed before pulling his shorts up as he flopped down beside her, wrapping her in his arms and pulling her close. 

They laid there, not talking, both trying to catch their breath as the experience still washed over them. 

“So,” (Y/n) commented, the first one to speak. 

“so,” Sans repeated. 

“Soulmates, huh?” She asked. 

“Yep,” he replied. 

“I didn’t know that monsters and humans could be soulmates,” she told him. “Kinda figured it would be impossible, you know, because of the whole uncertainty about the procreating thing…” 

“heh. don’t have to be able to procreate to be soulmates. if we can, we can. if we can’t, we could always talk about adoption if we wanna have a family. face it, babe; you’re stuck with me forever and ever.” 

“Oh no, now I’ll have to have my life filled with awful jokes,” she breezed sarcastically. “And the Grrrreat Papyrus’ awesome food! ...I hope… He’s a great cook, by the way. He thinks a bit outside the box of matching flavors sometimes, but he’s still great.” 

Sans let out a laugh. “yeah. my bro’s the best. let’s not talk about him while we’re still all covered in cum, though, huh?” 

“Oh, yeah,” (Y/n) chuckled, then let out a sigh of contentment. 

“ya happy right now?” Sans asked offhandedly. 

“Mmhm,” she hummed back. 

They were silent for another moment until Sans spoke this time. 

"not that i'm complainin' or anything, but, what were you doing here?" 

"Your brother asked me to come help him with picking out foods humans would like for- um, what did he call it?" She hummed as she tried to remember. "Oh! Bonding engagement. He wanted to plan a party." 

Sans looked puzzled for a moment before letting out a laugh. "stars, paps!" 

"What?" (Y/n) asked in surprise. 

"there- the only possible people that might be headed toward a bonding engagement would be…" He paused, his cheeks gaining a bright blue glow. "us…" 

"Wait- wat?!" (Y/n) asked in impressed shock. 

Sans couldn't stop laughing, squeezing her tight and nuzzling her. "he's too clever for his own good sometimes." 

"You mean to tell me that- that sneaky little bone boy tricked me into picking food for my -our- own engagement party without us even being engaged?!" 

Sans nodded, still chuckling and nuzzling her instead of speaking. 

(Y/n) sighed, sounding distraught. "Wow. That sneak. He needs to teach me some of his methods." 

Sans pulled back, leaving a skeleton kiss to her jaw. He looked down at her chest, trailing a phalange between her breasts. "he's probably not coming back til mornin'. how about i teach ya somethin' about souls in the meantime…" He suggested, his lewd intentions clear on his skull. 

**Notes for the Chapter:**

> If you enjoyed this, why not go check out my other stuff? Also, I have a tumblr.

**Author's Note:**

> I also posted a chapter of [Life with the Bone Brigade](https://archiveofourown.org/works/24584485) and [Captive Love](https://archiveofourown.org/works/23589097) today!  
> And I have a [tumblr](https://valkyrieofsmut.tumblr.com/).  
> 


End file.
